Wireless telegraphy and telephony.



E. H. COVLPITTS. WIRELESS TELEGBAPHY AND TELEPHONY- APPLICATION FILED JAN-21.1916. 1,256,983.

Patented Feb. 19, 1918.

TED STATES PA ora ion,

EDWIN H. COLPITTS. OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

WIEELESS TELEGRA-PHY AND TELEPHONY.

7 To all whom it may concern:

phy-and telephony.

Its object is to provide an improved method for the simultaneous transmission of telephone and telegraph signals and for their reception. This object is accomplished by transmitting telephone signals by means of a ure modulated wave (to be defined later in this specification), and by causing i the telegraph s1gna1s to destroy the purity of this wave.

In radio telephony it has been customary to supply to the antenna a wave of constant frequency and constant amplitude by means of a sending generator. The amplitude of this wave is then modulated in accordance with the signal to be sent. Now, it is well known that whena constant amplitude wave of frequency C (carrier wave) is modulated by means of another constant amplitude wave of low frequency S (signal wave) the resultant modulated Wave can be considered to be made up of three waves of constant amplitudes and of frequencies C+S, C, (3-8, and these waves are propagated independently through the ether to the receiving station. It will be evident that the second of the above waves, which does not contain the frequency" S of the modulating signal, represents a waste of power in the antenna, and

it has been proposed in applications Serial No. 64,502 and Serial No. 64,524, both filed December 1, 1915, to eliminate from the transmitting antenna the current of frequency C, and thereby to produce what will be called hereafter a pure modulated wave. The effect of the wave of frequency C is then introduced at the receiving station by means of a local generator of that frequency. The result of this method of telephony is to secure a much higher efliciency, since in practice thepower represented by currents of frequency C is in general larger than the power represented by the other components.

Specification of Letter; Iatent.

Patented Feb. 19, 1918.

Application filed January 27, 1916. Serial No. 74,576.

V The present invention proposes to utilize this method of telephony, and in addition to restore the wave of frequency C at the transmitting station in accordance with telegraph signals to be sent, so that telephone and telegraph messages may be sent simultaneously. A telegraph key is here arranged to superpose a wave of frequency C upon the outgoing signals, and thereby to destroy the purity of the modulation in accordance with the telegraph signals. At the receiving station a particular arrangement of apparatus is adopted which will be more completely described in connection with the drawing.

Figure 1 represents diagrammatically a sending station, and Fig. 2 a receiving station embodying the principle of the invention. Fig. 3 is a diagrammatic view showing a modification of the circuit arrangement at the sending station.

Referring to Fig 1, 1 is a generator of constant amplitude high frequency waves, 2 is a microphone, and transformers 3 and 4 are adapted toimpress both the high fre- (f uency waves generated by 1 and the low requency modulating waves generated by 2 upon the input circuit of a thermionic modulating device 5. The effect of this arrangement is to produce in the output circuit of the modulator 5 a high frequency current whose amplitude varies in accordance with the signals produced by the microphone 2. The transformer 6 serves to introduce these currents into a system of tuned circuits 7 and 8, whose functions are as follows:

The branch 7 is tuned to the frequency of the generator and therefore serves as a short circuit to currents of that frequency. The parallel arran ement of circuits 8 is so tuned as to offer a practically infinite impedance to currents of the generator frequency, and a low impedance to currents whose frequencies differ therefrom by the frequencies occurring in speech. There will therefore exist in the wlndings of transformer 9 practically no current of the gen- "erator or carrier frequency represented by C in the preceding discussion. -This transformer 9 impresses the modulated current upon the input circuits of the amplifiers 10, whose output circuits are connected to another set of amplifiers 11 arranged to furnish all the power to be :radiated. These amplifiers are finally coupled to the radiating antenna. 12. It will be clearthat tlns arrangement permits the radiatlon of only those waves whose frequencies differ from the frequency of the generator. 1

13 is a telegraph key and 14 a transformer coupled to the circult of the generator 1. When this key is closed the current of the carrier frequency is impressed directly upon the input circuits of the amplifiers 10, and currents of carrier frequency may then flow in the antenna. The resistance 15 is inserted in the ke circuit to avoid short-circuiting the amp ifier '10. It may also be desirable to insert a unilateral connection, such as a thermionic amplifier, in the key circuit to avoidthis. Such an arrangementis shown in Fig. 3, in which 25 represents the thermionic amplifier.

Fig.2 represents "a receiving station for use inconnection with the transmitting station of Fig. 1. In this, Fig. 16 is the receiving antenna which is coupled to the system of circuits 17 and 20, of which 17 is tuned to the carrier frequency, and 20 is similar to the circuit 8 of the firstfigure. It will be clear that when waves of carrier frequency are incident upon the antenna 16, they will produce an effect in the circuit 17, and will therefore be impressed upon the input circuit of the detecting tube 18, whose output circuit is coupled to a suitable translating device 19. When the key 13 of Fig. 1 is closed, thereby permitting the radiation of waves of the carrier frequency, an effect will be produced in the telegraph receiving device 19. On the other hand, currents of carrier frequency cannot appear in the transformer 24, which serves to couple the antenna circuits to the input terminals of a detector 21 whose output circuit supplies the telephone receiver 23. A local generator 22 of small power capacity is also coupled to the input circuit of this detector, and its function is to supply waves of the carrier frequency, eliminated at the transmitting station. This method allows the transmission of a telephone and telegraph message upon a single wave length.

It will be clear that by this method both telephone and telegraph signals may be transmitted and received independently of one another. It will also be obvious that many other systems of circuits may be de vised to accomplish this same object, and that the same may be used for transmission over wire lines instead of through space: and it is therefore desired not to limit this invention to the particular circuit arrangements shown.

What is claimed is:

1. The method of simultaneous telephony and telegraphy, which consists in transmitting telephone signals by means of pure modulated waves,

destroying the purity of 3. vA method of signaling which comprisesproducing a carrier wave, modulating such wave 1n accordance with speech, and el1m1- natmg portlons of the carrier wave component of the modulated wave for the purpose of code signaling.

' 4. A method of signaling which comprises producing a carrier ways at the transmitting station, modulatin such wave in accordance with signals, e iminating portions of the carrier frequency component, and separating at the receiving station the remaining portions of the carrier frequency component from the received Wave.

5. A signaling system including means for producing a carrier wave, signaling means for modifying said wave, a second signaling means, and means including said second signaling means for modifying the carrier frequency component of the modulated wave.

6. A signaling system including means for producin a carrier wave, signaling .means for modifying said wave, a second signaling means, and means'including said second signaling means for producing in the transmitted wave a signaling component of the carrier wave frequency.

7. In a. signaling system, means at the transmitting station for producin a composite wave one component of which is a pure modulated Wave and another component of which is a modified carrier wave,

and a receiver including means selectively responsive to. said components.

8. In a signaling system, means at the transmitting station for producing a composite wave one component of which is a pure modulated wave and another of which is a modified carrier wave, a receiver including indicating means responsive to one of said components, a second indicating means, and means preventing that one of the components which is responsive to the first indicating means from reaching the second indicating means.

9. In a signaling system, a receiving circuit, meanstherein responslve to the carrier wave component of the received wave, a second receiving circuit associated with .the first receiving circuit, means for preventing the carrier frequency component from reach- 11. A system of simultaneous telegraphy and telephony comprising a transmitting station including a generator of high frequency currents, means for modulating said currents in accordance with speech, means for eliminating the unmodulated part of said current whereby a pure modulated Wave is produced, means for superimposing upon said pure modulated Wave a Wave of the said generator frequency and a receiving station including means for detecting said waves.

In witness whereof, I hereunto subscribe my name this 24th day of January, A. D. 1916.

EDWIN, COLPITTS. 

